Induction heating processes may use ferromagnetic wires that heat up when exposed to alternating magnetic fields. For example, blankets that include ferromagnetic wires can be wrapped around thermoset composite parts. The blanket is then exposed to an alternating magnetic field, which induces alternating currents within the wires. The wires are heated due to I2R and magnetic hysteretic losses.
The magnetic permeability of the wires is one factor that can affect the heating performance of the blanket. Wires that have different magnetic permeability will exhibit different heating profiles within the same alternating magnetic field. This may cause hot spots in the blankets or temperature variations from one blanket to the next, which can cause problems in manufacturing processes that utilize ferromagnetic wires for induction heating. Generally, the magnetic permeability of ferromagnetic wires can change substantially during the manufacturing of the wires, with small changes in the composition of the wires and changes in how the wire-drawing process alters the grain size and orientation of the grains being some of the factors.
With the possibility that slight changes in the manufacturing process for the wires can produce substantial changes in the magnetic permeability of the wires, it is important to quickly and efficiently determine the magnetic permeability of samples of ferromagnetic wires that will be used to fabricate induction heating products, such as induction heating blankets.